Alkanes in aqueous systems. I. Exploratory investigations on the accommodation of C₂₀蜢C₃₃ n‐alkanes in distilled water and occurrence in natural water systems

Abstract

Abstract In order to understand more fully the mechanisms by which hydrocarbons may be mobilized for the ultimate formation of oil fields, the n‐alkane content of several aqueous systems was measured. Both laboratory and natural systems were studied. Exploratory measurements by gas liquid chromatography of total C 20 to C 33 n‐alkanes accommodated in distilled water, alkaline solutions, and solutions containing surfactants fell in the range of 1 to 10 mg/1. Millipore filtration markedly reduced the alkane content with a filter of 0.05 ॖ pore size removing as much as 97% of the accommodated alkanes. Alkaline solutions accommodated higher quantities of alkanes than the distilled water, but the addition of surfactants had little further effect. Natural waters had low total C 20 to C 33 n‐alkane content. Samples of surface waters showed values of 0.2 ॖg/1 in sea water, 0.5 ॖg/1 in lake waters, and 1.5 ॖg/1 in a river water. Coproduced oil field waters generally had a slightly higher n‐alkane content with values of 1 to 1.4 ॖg/1. Waters expressed from recent lake sediments contained up to 50 ॖg/1 of total C 20 蜢C 33 n‐alkanes. Addition of sodium bicarbonate and surfactants to the sediment prior to expressing water had little or no effect. The data presented appear to be of geochemical significance as they indicate that water has the capacity to accommodate significant quantities of n‐alkanes in a distribution remarkably similar to that of alkanes in the reference crude oil of A.P.I. Project 6.